Starter motor question.

[The Pikey]

As I am not using the MFU, I am fitting a relay for the starter button and figuring what fuse to use but I have come across something I don't understand.

 

Why does the solenoid draw massive amps when the main positive wire to the starter motor is disconnected but when it is connected and the motor can spin as normal the solenoid will draw 8 amps? So in other words, connect a 12v neg to the body of the starter and the pos to the small terminal on the solenoid and it will go click and then melt the wires.

 

cheers

jason

 

 

 

Edited by - jason fletcher on 30 Nov 2010 21:41:00

[Stationary M25 Traveller]

Silly question, but have you connected it up right ? Had a customer do this with a solenoid feeding a hosereel rewind motor. Had taken the feed to the motor from the small terminals for the coil on the solenoid.

 

Main fat feed wire for starter from battery to big terminal on solenoid, and then from the other to the starter. Small signal wire to small terminal on solenoid.

 

 

[Johnty Lyons]

I believe the solenoid only has two terminals one small [activation] and one large Battery Starter current it also has a braided cable out [other side of contacts] to Starter main terminal the output of the solenoid coil is going to earth via the braided connection rather that a mechanical metal to metal connection Path of least resistance . In the absence of a supply at that point to the Starter coil it is then passing through the starter windings thus the massive current requirement Most unusual but I have seen it before Completely strip and clean your starter and solenoid.

 

[The Pikey]

It's definatly wired up correctly and theres nothing wrong with the motor because I have two different new ones and they both act the same. If you were to disconnect the main terminal from the battery to your starter motor and tried to start the car I recon the solenoid would click as normal but it would draw big amps and blow the solenoid fuse. I'm just wondering why this would happen?

 

Jason

[Stationary M25 Traveller]

 

Well it shouldn't, as you are only connecting a feed to the coil of the solenoid, which would activate the solenoid .... And that is all.

[The Pikey]

SM25T

you are thinking like I am, it shouldn't, but I can assure you that it does!! Can't understand why. As I said, this is the same on two brand new but different models and different makes of starter motor.

 

I don't really need to know to get the thing running because when it's all connected it works perfectly but I do NEED to know to satisfy my curiosity.

 

cheers

Jason

 

 

[EFA]

Jason, Do the whole lot in a 32A cable. Forget relays, they are only a source of trouble.

 

 

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[The Pikey]

That would be a problem as the switch is only rated at 10 amps.

 

Jason

[Johnty Lyons]

Guys don't fret its normal on pre engaged starters as opposed to remote solenoids The earth path for the solenoid is through the main windings and without a Battery connected to the Main Starter contact your going to pull 30 amps If you need furthher clarification read This

[The Pikey]

Johnty

 

thanks for that I've read the info on your link and it all makes perfect sense to me now.

 

cheers

jason